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It's a little off topic, but I'm intrigued by the '87% of Americans can be uniquely identified by DOB, gender and zip code'. Given the size of the US's populati

by andrew1 17y ago

It's a little off topic, but I'm intrigued by the '87% of Americans can be uniquely identified by DOB, gender and zip code'. Given the size of the US's population and the relative scarcity of zip codes, this seems an incredible claim. The link in the article is broken so I can't read the paper. Even just thinking about the big cities, where I imagine virtually no one would be identifiable, that figure sounds impossibly high. Maybe the figure actually refers to just working adults or something like that. Does anyone have any more information about this, or access to the original paper?

andrew1 17y ago
Actually, I was thinking about DOB as being just the day and month, not day, month and year. If the year's included then this seems less far fetched, although I'd still be surprised if it's correct.
gojomo 17y ago
Back of the envelope: ~300 million Americans spread among ~100,000 zip codes yields an average of 3,000 people per zip code. So zip code alone narrows a person down to a set of around 3,000. Gender then to 1,500. That's only 4.2 years worth of unique birthdays! Unless the zip code is dominated by a certain age group (as around a college campus), there should be a lot of unique birthdays, since those will be drawn from a range of many decades. Do densely-packed cities change things much? A bit, but they probably also have helpful age-diversity. San Francisco has 800,000 people and 25 zip codes -- 32,000 per zip code; 16,000 per gender; 16,000 unique birthdays would cover 45.2 years. So there are sure to be more collisions, but still many unique zip/sex/DOB combinations. And for all the zip codes with < 3,000 residents, the people uniquely addressable could be 97, 98, 99%. If we take zip+4, it's all over. My 12-unit apartment building has 2 zip+4 codes all by itself, so zip+4 identifies a group of < 12 people.

by andrew1 17y ago

andrew1 17y ago

Actually, I was thinking about DOB as being just the day and month, not day, month and year. If the year's included then this seems less far fetched, although I'd still be surprised if it's correct.

gojomo 17y ago

Back of the envelope: ~300 million Americans spread among ~100,000 zip codes yields an average of 3,000 people per zip code. So zip code alone narrows a person down to a set of around 3,000. Gender then to 1,500. That's only 4.2 years worth of unique birthdays! Unless the zip code is dominated by a certain age group (as around a college campus), there should be a lot of unique birthdays, since those will be drawn from a range of many decades. Do densely-packed cities change things much? A bit, but they probably also have helpful age-diversity. San Francisco has 800,000 people and 25 zip codes -- 32,000 per zip code; 16,000 per gender; 16,000 unique birthdays would cover 45.2 years. So there are sure to be more collisions, but still many unique zip/sex/DOB combinations. And for all the zip codes with < 3,000 residents, the people uniquely addressable could be 97, 98, 99%. If we take zip+4, it's all over. My 12-unit apartment building has 2 zip+4 codes all by itself, so zip+4 identifies a group of < 12 people.